Catheters formed of a biocompatible plastics material are sometimes implanted in patients to relieve various symptoms and/or to assist in medical procedures. For example, central venous catheters have been implanted into a patient's vein during vascular surgery. One problem associated with such implanted catheters, however, is that a fibrin sheath (which is a deposit of fibrin and platelets) may form on the implanted catheter, initially at the entrance site into the vein and then along the length of the catheter. While it usually takes weeks to months for the fibrin sheath to form, it has been reported to form in as little as 24-48 hours following implant.
The fibrin sheath can cause catheter dysfunction, usually being manifested by the physician being able to infuse through, but not to aspirate from, the catheter. Intraluminal urokinase may then be administered several times to exclude the possibility of intraluminal clotting. If intraluminal urokinase treatment is ineffective, fluoroscopy may then be performed to allow the physician to evaluate catheter tip location and to obtain evidence of fibrin sheath formation.
Once the presence and extent of the fibrin sheath have been identified, the physician must take the necessary steps to remove the sheath from the implanted catheter. While it is conceivable that the implanted catheter may be removed and replaced surgically, it is more desirable for the fibrin sheath to be removed without surgical removal of the implanted catheter.
Presently, there are basically two approaches which may be employed without removal of the implanted catheter. The first approach involves introducing percutaneously a goose-neck snare (e.g., a snare device generally disclosed in U.S. Pat. No. 5,171,233 to Amplatz et al, the entire content of which is incorporated expressly hereinto by reference) into the patient's groin area. The snare is then advanced through the patient's femoral vein to the catheter implant site, at which time it is manipulated so that the snare encircles the distal end of the implanted catheter so that the fibrin sheath may be stripped therefrom. While the fibrin sheath which is stripped from the distal end of the implanted catheter travels to the patient's lung, surgical removal has been shown to result in embolization as well.
Another technique that has been employed to strip fibrin sheaths from the distal ends of implanted catheters is to introduce a J-tipped wire intraluminally through the implanted catheter. Rotation of the J-tipped wire about the distal end of the implanted catheter will thus strip a portion of the fibrin sheath therefrom. While this technique is advantageous since the implanted catheter serves as a guide passageway (i.e., separate incisions to access the femoral vein are unnecessary), the J-tipped wire is typically only capable of removing less than all of the fibrin sheath from the implanted catheter due to its size limitations.
What has been needed in this art, therefore, is a medical device which is capable of being guided intraluminally through an implanted catheter, but which is capable of removing substantially all of the fibrin sheath that may have formed at the catheter's distal end. It is towards fulfilling such a need that the present invention is directed.
Broadly, the present invention is embodied in medical devices having a snare loop for removing patient-internal biological material from an implanted catheter (e.g., a fibrin sheath which may form at the distal end of a venous catheter) which may be inserted intraluminally through the catheter during a medical procedure. The tubular member has a length sufficient to allow its distal end portion extend beyond the distal end of the patient-internal catheter. A central wire element is movably positioned within the elongate tubular member and has a sufficient length so that its terminal end potion extends distally beyond said distal end of said tubular member.
Importantly, a snare wire is provided such that one of its ends is attached to the central wire with the other end attached to the distal end of said tubular member after completing approximately 360.degree. wrap around the tubular member between the ends. The snare wire, between its attached ends, will include a segment which extends proximally at an acute angle and may therefore be located upon manipulation of the device adjacent the distal end of the patient-internal catheter. Relative rotation between the central wire and the tubular member (e.g., by rotating the central wire about its longitudinal axis while maintaining the tubular member stationary or vice versa) causes said snare wire segment to be wrapped around said distal end of the patient-internal catheter. Distal advancement of this wrapped snare wire segment relative to said distal end of the patient-internal catheter will therefore strip the biological material therefrom.
Further aspects and advantages of this invention will become more clear after careful consideration is given to the following detailed description of the preferred exemplary embodiment thereof.